The old buildings I know that approximately reach this number of rooms (8 bedrooms/guest/workrooms) are usually rather two-family houses or were used as multi-generational houses (with more or less well-separated living units). That means where grandma lived in the house for a long time or something similar. From the rural area where I grew up, I partly know it like that (there are also some older farmhouses, for example, where the barn or similar was later converted into living space). But I wouldn’t call it "the norm" either, and many houses there are maybe even a bit older than the thread starter imagines. And I wouldn’t describe it as a classic single-family house anymore.